Add .NET Framework support to Verify.TUnit (#1426)

Author: thomhurst

src/Verify.TUnit/Verify.TUnit.csproj

@@ -1,8 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net8.0;net9.0;net10.0</TargetFrameworks>
-    <SignAssembly>false</SignAssembly>
+    <TargetFrameworks Condition="'$(OS)' == 'Windows_NT'">net472;net48</TargetFrameworks>
+    <TargetFrameworks>$(TargetFrameworks);net6.0;net7.0;net8.0;net9.0;net10.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>